Vehicle muffler and method of assembly

ABSTRACT

A muffler for vehicles propelled by internal combustion engines. The muffler is formed of two pieces, preferably metal stampings, in which the various chambers and passages are indented or embossed. The two pieces are joined at their peripheral edges. The muffler is tuned by adjusting the relative size and arrangement of chambers and passages. In one modification the position of the pieces may be adjusted relatively to each other to permit variable tuning.

[ 1 Feb. 1, 1972 United States Patent Thiele [54] VEHICLE MUFFLER ANDMETHOD OF 3,158,222 [1964 Richmond Betts et ....181/62 X Nordquest eta1.

ASSEMBLY [72] Inventor: Robert E. Thiele, Franklin Township,

Westmoreland County, Pa.

[73] Assignee: United States Steel Corporation 632,013 11/1949GreatBritairl.....

M30119 1,012,463 12/1965 GreatBritain.......................:... [21]App1.No.: 889,102

[22] Filed:

Primary Examiner-Robert S. Ward, Jr.

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0 5 mm U wlF 2 8 5 55 r1 dented or embossed. The two ieces are 'oined attheir l l 6 names Cited peripheral edges. The muffler is tuned byadjusting the relative UNITED STATES PATENTS size and arrangement ofchambers and passages. in one modification the position of the piecesmay be adjusted relatively to each other to permit variable tuning.

181/61 X .....181/61X 7/1964 Tranel 3 8 Claims, 5 Drawing Figures Harley2,860,722 11/1958 Gerstung.... 3,140,755

PATENTED FEB 1 1972 SHEET 2 0F 2 NW Db l mb m6 Vb m QR VEHICLE MUFFLERAND METHOD OF ASSEMBLY This invention relates to improved mufflers forvehicles propelled by internal combustion engines and to improvedmethods of assembling and tuning such mufflers.

A conventional muffler includes a double-walled metal casing and aplurality of baffles, tubes or pipes within the casing. The spacebetween the two walls commonly is filled with asbestos. The internalparts are spot-welded to the casing, and the end walls and wrap of thecasing are crimped or lockseamed together. A typical conventionalmuffler has a total of 13 pieces. A muffler usually fails throughcorrosion caused by an accumulation of highly corrosive condensatewithin its interior. Although the parts are galvanized, this method ofconstruction leavesraw unprotected edges which are exposed to condensateand corrode rapidly. This corrosion leaves internal parts unsupportedand allows them to rock and causes mechanical failure of externaljoints. Conventional muffler design and fabrication methods are poor inresisting corrosion and often produce conditions which acceleratefailure.

A muffler not only lowers the noise of an engine to an acceptable levelof about 80 to '85 decibels, but commonly is tuned to give a distinctivesound to each make of vehicle on which it is installed. I-Ieretofore theparts of the muffler have been relatively fixed, and tuning could beaccomplished only by arranging the internal parts in the proper relationwhen the muffler is manufactured. This necessitates a different mufflerconstruction for each make of vehicle if each is to have its owndistinctive sound.

An object of my invention is to provide improved mufflers and assemblingmethods in which the muffler is formed of only two pieces, whereby themuffler is simpler, of lighter weight, and more economical tomanufacture than conventional muffiers.

A further object is to provide improved mufflers and assembling methodsin which unprotected edges and crevices are avoided, whereby the mufflerhas better resistance to corroslon.

A further object is to provide improved mufflers and assembling methodswhich facilitate tuning the muffler to produce the sound distinctive forany particular make of vehicle.

A further object is to provide improved mufflers and assembling methodswhich enable muffler parts to be standardized to a greater extent thanheretofore.

In the drawings:

FIG. I is a diagrammatic perspective view of the bottom piece of atwo-piece muffler constructed in accordance with my invention toillustrate the principles;

FIG. 2 is a perspective view of one form of actual muffler constructedin accordance with my invention;

FIG. 3 is a top plan view of the bottom piece of the muffler shown inFIG. 2;

FIG. 4 is a perspective view of a modified muffler constructed inaccordance with my invention to permit variable tuning; and

FIG. 5 is a fragmentary vertical sectional view of a mufflerillustrating one way in which I may join the pieces.

FIG. 1 shows the bottom piece of a possible two-piece mufflerconstructed in accordance with my invention. The piece preferably is ametal stamping, although it can be cast or molded or formed of othermaterials, such as plastic or ceramic. The piece illustrated hasrectangular indentations and 12, a fiat rectangular area 13 betweenindentations, and a peripheral lip 14. The flat area 13 has a passage 15of semicircular cross section affording restricted communication betweenthe two indentations. The ends of the piece have indented extensions 16and 17 which communicate with the respective indentations 10 and 12. Thedimensions, locations, shape, and number of indentations and passagesmay vary. Such variations produce different expansion and contraction ofsound waves entering the muffler and various frequency attenuations toproduce the desired sound output, as hereinafter explained. Preferablythe indentations l0 and 12 have rounded edges, as indicated at 18. lassemble this piece with a mating top piece, and join the two pieces byany suitable means at the periphery, such as welding the two lips 14 orjoining them adhesively, or by a novel means hereinafter described inconnection with FIG. 5. In the muffler thus assembled, the indentationsl0 and 12 afford first and second mixing chambers, and the extensions I6and 17 afford an inlet and outlet respectively for exhaust gases from anengine.

FIGS. 2 and 3 show an actual construction of two-piece muffler inaccordance with my invention designed to produce the soundcharacteristic of a particular make of automobile of recent model. Themuffler comprises mating top and bottom pieces 21 and 22, againpreferably formed of metal stampings. indentations in the pieces form afirst mixing chamber 23 adjacent the inlet end, a second mixing chamber24 adjacent the outlet end, a distribution chamber 25 between the twomixing chambers, and lengthwise passages 26 adjacent each side edge. Theends of the pieces have indented extensions 27 and 28 which communicatewith the mixing chambers 23 and 24 respectively and serve as an inletand outlet for exhaust gases. Series of embossments 30 afford restrictedcommunication between each side of the first mixing chamber 23 and theadjacent passage 26. Similar embossments 31 afford restrictedcommunication between passages 26 and the second mixing chamber 24. Thedistribution chamber 25 is open at each side throughout its length tothe adjacent passage 26. The two pieces 21 and 22 have peripheral lips32 which arejoined by any suitable means as explained in the descriptionof FIG. 1.

FIG. 3 shows the bottom piece 22 in more detail. Besides theindentations and embossments already described, the bottom piece has twotransversely spaced embossments 34 separating the first mixing chamber23 and the distribution chamber 25, and an unbroken transverseembossment 35 which forms a wall separating the distribution chamber andthe second mixing chamber 24. The embossments 30 define series ofrestricted openings 36 which slant from the first mixing chamber 23toward the passage 26. The embossments 31 define series of restrictedopenings 37 which slant from the passage 26 toward the second mixingchamber 24. In each instance the openings 36 and 37 slant in thedirection of gas flow. The opening between the two embossments 34 isdesignated 38.

Noises which accompany exhaust gases into the muffler commonly have anoise level of at least 125 decibels and are composed of bothhigh-frequency and low-frequency sound waves. The muffler lowers thenoise level to about to decibels, and suppresses undesirable sound wavecomponents. The objective is to produce a characteristic pleasing soundwhich is distinctive for any particular make and model vehicle. Usuallyhigh-frequency sound waves are suppressed to avoid a tinny or metallicsound. However, if high-frequency waves are eliminated together themuffler produces an undesirable hollow sound. The resultant sound outputusually sought is a smooth sequence of attenuated low-frequency boomswith enough high-frequency sounds to produce a pleasing distinctivetone.

FIG. 3 also shows the pattern which sound waves follow within themuffler shown in FIG. 2. High-frequency waves tend to travel in straightcourses. Hence incoming highfrequency waves mostly pass directly throughthe first mixing chamber 23 and opening 38 into the distribution chamber25, as indicated by arrows 39. Such waves echo against the embossrnent35, which lowers their energy level. The weakened high-frequency wavespass through both sides of chamber 25 into passages 26, as indicated byarrows 40. Low-frequency waves tend to spread sideways. Hence incominglow-frequency waves pass from the first mixing chamber 23 throughopenings 36 into passages 26, as indicated by arrows 41. The high andlow-frequency waves blend within passages 26 and pass through openings37 into the second mixing chamber 24, as indicated by arrows 42. Thefinal sound output from the muffler of course depends on the relativesize and shape of the chambers, passages and openings.

In the modification shown in FIGS. 2 and 3, the low point of the muffleris located near the outlet end to permit condensate to drain thereto.The area around the low point can be specially reinforced to prolong theuseful life of the muffler, or the muffler can be equipped with aspecial drain to carry away condensate from its low point. Anotherpossibility is to locate the low point near a hot part of the muffler sothat condensate is revaporized. With my method of construction, I canlocate the low point anywhere desired within the muffler.

FIG. 4 shows a two-piece muffler of modified construction in accordancewith my invention designed to permit variable tuning. The mufflercomprises mating top and bottom pieces 45 -and46, again preferablyformed of metal stampingsrlndentations' in the top piece form a firstmixing chamber 47 adjacent the inlet end, a second mixing chamber 48adjacent the outlet end, a distribution chamber 49 between the twomixing chambers, and a blind chamber 50. A passage 51 affordscommunication between the first mixing chamber 47 and thedistributionchamber 49. Passages 52 and 53 afford communication betweenthe distribution chamber and the second mixing chamber 48 and betweenthe distribution chamber and the blind chamber 50 respectively. Themuffler has an inlet 54 formed by indentations in its two pieces, and asimilar outlet not shown. The two pieces, although mating, are notnecessarily alike, but the bottom piece 46 may provide chambers of otherconfigurations, such as the chamber 55 illustrated. The two pieces haveperipheral lips 56 which are joined as in the embodiments alreadydescribed.

l tune the muffler of FIG. 4 by adjusting the position of th top andbottom pieces 45 and 46 relatively to each other. In

the construction illustrated the pieces are arranged for adj ustmentlengthwise of the muffler, and the top piece carries a scale 57-toindicate the relative position it should occupy for differentcharacteristic sounds. If the muffler is massproduced, the scale can beused to adjust the pieces to the proper setting for any make of.vehicle, thereby permitting standardization. The pieces can be extendedat the lips and at the indentations which form the inlet and outlet, andtrimmed off flush as shown after theyare in their final position ofadjustment. With this modification it is possible also to tune themuffler and join the two pieces after the muffler has been installed ona vehicle. This is a particularly desirable feature for replacementmufflers to enable a muffler formed of standardized parts to sound righton any make of vehicle. Although I show two pieces adjustablelengthwise, it is apparent they could be adjustable in other directions,such as transversely or by relative rotation.

FIG. illustrates a preferred way of joining the two pieces of my mufflerapplicable to nonadjustable forms. The peripheral lips 60 and 61 of thismuffler have interfitting indentations 62 and 63. The lower lip 60 hasan upstanding flange 64 to provide stiffness. The lower lip 60 has anupstanding flange inner surfaces of the two pieces preferably have aprotective coating such as porcelain, which may be applied by dipping orspraying. l interpose a layer 65 of brazing material between theindentations 62 and 63. The brazing material may be brass and may be inpowder, strip or rod form. I place the assembled muffler in a porcelainbaking oven and fire it. The porcelain acts as a flux and the two piecesare brazed together while they are porcelainized, but if the mufiler isnot porcelain coated, I can add a suitable flux. lam aware that mufflershave been porcelainized previously, but the porcelain coating could beapplied only after the muffler was totally assembled by flowing theporcelain material through the muffler. This is an expensive operation,and did not always produce a uniform coating.

From the foregoing description it is seen that my invention provides amuffler of simple two-piece construction, the individual pieces of whichcan be formed as inexpensive stampings. The muffler not only hassuperior corrosion resistance, but is readily tuned to give the noiselevel and characteristic sound desired for any particular vehicle.

lclaim:

l. A vehicle mufiler comprising mating top and bottom pieces and meansjoining-said pieces at their peripheral edges, said pieces havingindentations defining one or more mixing chambers, and an inlet andoutlet communicating with said chambers, whereby the level of noiseaccompanying gases introduced through said inlet' is lowered and theresultant noise tuned to be characteristic of the vehicle, a low pointbeing provided in the muffler to facilitate drainage.

2. A muffler as defined in claim 1 in which said pieces are metalstampings and the means joining the stampings include lips extendingaround their peripheries, and in which said indentations define at leasttwo mixing chambers and means affording restricted communication betweensaid chambers.

3. A muffler as defined in claim 2 in which said pieces can be adjustedrelatively to each other to permit variable tuning.

4. A vehicle muffler comprising:

mating top and bottom metal stampings having lips extending around theirperipheral edges and a plurality of indentations;

means joining said stampings at said lips;

said indentations defining first and second mixing chambers, adistribution chamber between said mixing chambers, and lengthwisepassages along each side of said chambers, said distribution chambercommunicating with one of said mixing chambers and with said passages,said passages having restricted communication with both said mixingchambers; and

an inlet and an outlet communicating with said first and second mixingchambers respectively,

whereby the level of noise accompanying gases introduced through saidinlet is lowered and the resultant noise tuned to be characteristic ofthe vehicle.

5. A muffler as defined in claim 4 in which said pieces have embossmentsbetween said mixing chambers and said passages defining restrictedopenings which slant in the direction of gas flow.

6. A muffler as defined in claim 5 in which the wall between saiddistribution chamber and said second mixing chamber is adapted to directhigh-frequency sound waves into said passages, and said restrictedopenings are adapted to conduct low-frequency sound waves into saidpassages, where the high and low frequency sound waves blend.

7. A vehicle muffler comprising mating top and bottom pieces having lipsextending around their peripheral edges, said lips having interfittingindentations, brazing material interposed between said interfittingindentations joining said pieces, said pieces having indentationsdefining one or more mixing chambers and an inlet andoutlet-communicating with said chambers, whereby the level of noiseaccompanying gases introduced through said inlet is lowered and theresultant noise tuned to be characteristic of the vehicle.

8. A muffler as defined in claim 7 in which said pieces are metalstampings internally coated with porcelain.

UNITED STATES MTENT owner QERHHQAEE OF @ORREQTWN Patent No. 3,638,756 1Dated February 1, 1972 IIWEMOHS) Robert'E. Thiele It iscertified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 2, line 51, "together" should read altogether Column 3 lines 51and 52, cancel "lower lip 60 has an upstanding flange".

Signed and sealed this 31st day of October 1972.

(SEAL) Attest:

EDWARD MOFLETCHERJR, ROBERT GOTTSCHALK Arresting Officer Commissioner ofPatents :ORM (10459) usco MM-Dc 60376-P69 [1.5. GOVERNMENT PRINTINGOFFICE: I969 0-356-35,

UNITED swims PATENT @FMCE CERHMQATE @EF CQRRIEQTWN Patent No. 3 638 756Dated February 1, 1972 T T n Inventor-(s) RODQWC E, Imele It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 2, line 51, "together" should read M altogether o Colman 3, lines511. and 52, cancel "lower lip 60 an upstanding flange" Signed. andsealed this 318% day of October 1972.

(SEAL) Atteet:

GOTTSCI-KALK (Joisioner of Patents @WARD FEOFLETCBER,JRQ Ac'bestingOfficer DRM P -10 (1 USCOMM-DC 60S76-P69 US. GOVERNMENT PRINTING OFFICE:I569 O-366-334,

1. A vehicle muffler comprising mating top and bottom pieces and meansjoining said pieces at their peripheral edges, said pieces havingindentations defining one or more mixing chambers, and an inlet andoutlet communicating with said chambers, whereby the level of noiseaccompanying gases introduced through said inlet is lowered and theresultant noise tuned to be characteristic of the vehicle, a low pointbeing provided in the muffler to facilitate drainage.
 2. A muffler asdefined in claim 1 in which said pieces are metal stampings and themeans joining the stampings include lips extending around theirperipheries, and in which said indentations define at least two mixingchambers and means affording restricted communication between saidchambers.
 3. A muffler as defined in claim 2 in which said pieces can beadjusted relatively to each other to permit variable tuning.
 4. Avehicle muffler comprising: mating top and bottom metal stampings havinglips extending around their peripheral edges and a plurality ofindentations; means joining said stampings at said lips; saidindentations defining first and second mixing chambers, a distributionchamber between said mixing chambers, and lengthwise passages along eachside of said chambers, said distribution chamber communicating with oneof said mixing chambers and with said passages, said passages havingrestricted communication with both said mixing chambers; and an inletand an outlet communicating with said first and second mixing chambersrespectively, whereby the level of noise accompanying gases introducedthrough said inlet is lowered and the resultant noise tuned to becharacteristic of the vehicle.
 5. A muffler as defined in claim 4 inwhich said pieces have embossments between said mixing chambers and saidpassages defining restricted openings which slant in the direction ofgas flow.
 6. A muffler as defined in claim 5 in which the wall betweensaid distribution chamber and said second mixing chamber is adapted todirect high-frequency sound waves into said passages, and saidrestricted openings are adapted to conduct low-frequency sound wavesinto said passages, where the high and low frequency sound waves blend.7. A vehicle muffler comprising mAting top and bottom pieces having lipsextending around their peripheral edges, said lips having interfittingindentations, brazing material interposed between said interfittingindentations joining said pieces, said pieces having indentationsdefining one or more mixing chambers and an inlet and outletcommunicating with said chambers, whereby the level of noiseaccompanying gases introduced through said inlet is lowered and theresultant noise tuned to be characteristic of the vehicle.
 8. A muffleras defined in claim 7 in which said pieces are metal stampingsinternally coated with porcelain.